Known roller bearings include various means for guiding and positioning rollers. Such roller bearings typically include an inner ring that provides a substantially spherical inner race surface, a pair of outer race surfaces having convex curvatures, and a pair of oppositely inclined rows of symmetrical hourglass-shaped rollers. This type of bearing may be referred to as an hourglass roller bearing.
Hourglass roller bearings may be used in oscillatory applications, such as in aircraft flight control surfaces. In such applications, for example, rotation of the outer ring relative to the inner ring may be limited within a window or rotation for example 45 degrees. In such applications it may be desired that the rollers precess or index, so that they are each cycled through the load zone. Cycling the rollers results in use of the entire race surface of each of the rollers to extend rolling contact fatigue life. Cycling the rollers also redistributes grease for improved lubrication of the bearing unit which in turn reduces fretting damage and improves the bearing unit's resistance to raceway corrosion. Typical cages can inhibit the precessing or indexing of the rollers.